The invention relates to a bed exit alarm and, more particularly, to a bed exit alarm using pressure feedback from side bolsters on a support surface.
Care givers in a hospital or other treatment/care facility often must be able to know when a patient remains in a medical bed or chair, or has removed themselves. Unassisted bed exits can cause patient harm or injury, even losing patients in the facility if the patient becomes disoriented.
It is desirable to have some sort of notification/monitoring system of these unplanned bed/chair exits. There are many systems that claim to do this.
U.S. Pat. Nos. 4,484,043 and 4,565,910 describe devices that use a switch mechanism which is used to open and close a circuit to indicate the exit from a bed. The switches are basically two long conductors that make contact when the patient's body weight is on them. A closed switch indicates that the patient is in bed. The reverse happens when the patient exits; the conductors move apart, the switch opens and a bed exit is indicated.
U.S. Pat. No. 6,778,090 describes a capacitive array housed within a thin mat, which is placed either under the patient or under the mattress itself. This capacitance device detects a dielectric shift induced capacitive changes brought about by either the presence or absence of a patient on the bed.
U.S. Pat. No. 5,410,297 also describes a capacitive sensor pad device with a foam and aluminum foil pad. The pad under the patient has weight responsive capacitance characteristics that vary with the patient's weight and movement.
U.S. Pat. Nos. 4,179,692 and 4,295,133 disclose a system in which an on/off switch generates binary signals in response to the movements of the patient in and out of bed.
U.S. Pat. No. 4,700,180 also uses a binary generating sensor. When the patient lies down, the first switch position is established. When the patient exits the bed, the switch changes to its alternate state, thereby providing a binary signal.
U.S. Pat. No. 5,235,319 describes another capacitor sensor device at a predetermined location in the bed used in conjunction with a monitoring circuit system.
All of the above devices and other similar art have several disadvantages. The first and most problematic is that these sensing or capacitance devices are placed in pads which are either directly under the patient or under the mattress. If the pad is placed directly under the patient, it must be very thin and flexible so as not to increase the pressure on the bony protuberances of the patient. If the sensing pad is under the mattress, it loses its effectiveness as all inputs and outputs from the sensing pad must travel through the mattress. For instance, as the patient shifts their weight to exit the bed, due to the thick and “stiff” mattress, the weight distribution might be significantly distorted, causing the bed exit alarm not to work properly. Secondly, there is a lot of sophisticated circuitry and there are many components required to make these complicated capacitance or switch systems work, leading to higher costs, and greater chances of malfunctions.